A cashel is a ringfort built from stone rather than earth, its enclosing wall serving the same purpose as the earthen banks of a ráth: to define a farmstead, assert ownership, and provide a degree of protection during the early medieval period, roughly between the fifth and twelfth centuries. Thousands of these structures survive across Ireland in various states of preservation, but each one marks a specific patch of ground where someone chose to live, farm, and build in permanence.

Glenkeen is a quiet townland in Mayo, and the cashel there belongs to a category of monument that once would have been a working agricultural enclosure, probably home to a single family of some local standing. Stone-built ringforts tend to cluster in areas where building material was readily available, and the west of Ireland, with its exposed limestone and field-clearing traditions, preserves a disproportionate number of them. Beyond its classification and location, the documentary record for this particular site is thin, and the details that would place it more firmly in time or connect it to named individuals or events are not currently available.